Wave winding for dynamo electric machine

ABSTRACT

A dynamo electric machine having four pole pieces and windings through which electric current can be passed to polarize the pole pieces, the winding being formed by physically deforming a pair of coils having equal length, the deformation of the coils producing four substantially straight coil portions which are disposed between adjacent pole pieces respectively. The end connectors for each coil are spaced by 180*.

United States Patent Seilly 1 Mar. 21, 1972 WAVE vWINDING FOR DYNAMOFOREIGN PATENTS OR APPLICATIONS ELECTRIC MACHINE I 19,732 2/1936Australia ..3lO/l [72] Inventor: Alec Harry Seilly, North Wembley, En-1,188,515 4/ 1970 Great Britain ..3l0/ 179 gland OTHER PUBLICATIONS [73]Assignee: C.A.V. Limited, Birmingham, England Siskind, Induction Motors,McGraw-Hill Book Co., 1958, pp. [22] Filed. June 12, 1970 8 84 66 67.[21] App]. No.: 45,885

Primary Examiner-William M. Shoop, Jr. Assistant Examiner-B. A Reynolds[30] Foreign Application Priority Data Attorney-Holman & Stem June, 1969Great Britain ..30,l16/69 [57] ABSTRACT [52] US. Cl ..3l0/180, 310/202[51] Int. Cl. ..H0lv 3/28 A dynamo electric machine having four polepieces and [58] Field of Search ..310/ 179, 207, 180, 184, 188, windingsthrough which electric current can be passed to 242/11 polarize the polepieces, the winding being formed byphysically deforming a pair of coilshaving equal length, the defor- [56] References C'ted mation of thecoils producing four substantially straight coil UNITED STATES PATENTSportions which are disposed between adjacent pole pieces respectively.The end connectors for each coil are spaced by 2,289,673 7/1942Neumeister et al ..310/179 18() 2,622,217 12/1952 Anderson ....310/1663,328,617 6/1967 Preece ..310/180 1 Claims, 3 Drawing FiguresPATENTEDMARZ] m2 3.651356 JMJL ZLZ ATTORNEYS WAVE WINDING FOR DYNAMOELECTRIC MACHINE This invention relates to dynamo electric machines ofthe kind comprising an armature having a commutator and a fieldstructure including four pole pieces and windings through which electriccurrent can be passed to polarize the pole pieces. 7

In known dynamo electric machines of this kind the windings areindividually wound and have an equal number of turns. In this caseproviding that the current flowing in each winding is equal then thenumber of ampere turns will also be equal. This form of constructionshas been supersededin certain types of machine by a wave winding inwhich a single coil is provided which is physically deformed toelongated generally annular form so that between each pair of polepieces there is disposed a straight portion of coil, the adjacentstraight sections being interconnected by curved end portions. With thisarrangement the number of ampere turns is unequal. For a single turncoil the difference in the number of ampere turns is at a maximum and ifin one pair of adjacent coil portions the number of ampere turns is 1then in the other pair of coil portions the number of ampere turns willbe 1.5. This difference decreases as more turns are provided on the coilhowever, the number of turns which can be provided is limited so thatthe flux density in each pole piece can never be equal. This appliesparticularly in the case of a series connected motor and can lead topoor commutation. The object of the invention is to provide a machine ofthe kind specified having a wave winding in which the flux density ineach pole piece will be substantially equal.

According to the invention in a dynamo electric machine of the kindspecified the windings are formed by a pair of coils of equal lengthwhich are deformed so as to define four straight coil portions disposedbetween adjacent pole pieces respectively, the ends of the coils beingdisposed at 180 relative to each other.

One example of a dynamo electric machine inaccordance with the inventionwill now be described with reference to the accompanying drawings inwhich:

FIG. I is a part sectional side elevation of a series wound motor,

FIG. 2 shows a developed view of the field windings of the conventionalmachine, and

FIG. 3 shows a developed view of a machine having a winding modified inaccordance with the invention.

Referring to FIG. 1 the dynamo electric machine includes four polepieces which are secured to the internal periphery of an annular statorstructure 11 at equiangularly spaced intervals. Rotatably supportedwithin the stator structure 11 is an armature 12 having a commutator 13with which cooperates a brush set 14 through which electric current canflow to the armature. The particular form of dynamo electric machineunder consideration is an electric starting motor for an internalcombustion engine and in this arrangement the field windings and thearmature are connected in series.

As shown in FIG. 2 the field winding of known machines comprises a coil15 having a single turn. The coil is deformed so as to define straightportions 16 which lie between adjacent pole pieces 10 respectively. Iffor example, the current flowing in the winding equals one amp., thenthe effective ampere tumsin two adjacent pole pieces 10 is also 1 but inthe other two pole pieces 10a it equals 1.5. This difference is due tothe endportions of the coil. The degree of unbalance can be lessened byproviding more turns on the coil however, the number of turns'which canbe provided is limited and the resulting unequal flux density in thepole pieces can lead to poor commutation.

In order to avoid the unequal magnetization of the pole pieces thewinding is formed by two separate coils l7, 18 of equal length. Theconnecting leads to the two coils are spaced 1 by 180 and in this mannerthe pole pieces are magnetized to the same extent providing the currentflowing in each coil is equal. In the particular example if the currentflowing in each coil is one-half A., then the effective ampere turns ineach pole piece equals 1.25. I

It will be understood that in practice the coils Will be provided withmore than one turn and that they may be connected in parallel with eachother or in series.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. A dynamo electric machine of the kind comprising an armature, acommutator mounted on the armature, brushes bearing on the commutatorand through which electric current flows in the armature, a fieldstructure comprising four pole pieces disposed about the armature and afield winding mounted about the pole pieces for magnetically polarizingsame, said field winding including straight portions disposedintermediate adjacent pole pieces, adjacent straight portions beinginterconnected at one end by means of curved portions of the winding todefine an annular wave winding having portions extending adjacent threesides of each pole piece, the winding comprising a pair of coils, eachcoil having a lead-in portion and a leadout portion said portions beingadjacent each other, and the coils being displaced relative to eachother by an amount so that the lead-in and leadout portions of one coilare disposed at a position in the winding displaced by 180 relative tothe lead-in and leadout portions of the other coil.

1. A dynamo electric machine of the kind comprising an armature, acommutator mounted on the armature, brushes bearing on the commutatorand through which electric current flows in the armature, a fieldstructure comprising four pole pieces disposed about the armature and afield winding mounted about the pole pieces for magnetically polarizingsame, said field winding including straight portions disposedintermediate adjacent pole pieces, adjacent straight portions beinginterconnected at one end by means of curved portions of the winding todefine an annular wave winding having portions extending adjacent threesides of each pole piece, the winding comprising a pair of coils, eachcoil having a lead-in portion and a leadout portion said portions beingadjacent each other, and the coils being displaced relative to eachother by an amount so that the lead-in and leadout portions of one coilare disposed at a position in the winding displaced by 180* relative tothe lead-in and leadout portions of the other coil.